Future generation (e.g., Fifth Generation (5G)) cellular communications networks that operate on millimeter frequencies will use a large number of antennas, particularly at the base stations but potentially also at the wireless devices. The antennas utilized by a particular radio node (e.g., a base station or a wireless device) are implemented as an antenna array. The number of antenna elements in such an antenna array is expected to be 128 or even higher. Further, at millimeter frequencies, the antenna array is likely to be integrated with the Radio Frequency (RF) components on a single substrate (e.g., a single Printed Circuit Board (PCB)). A substrate on which the antenna array and, in some implementations, the RF components are integrated is referred to herein as a Substrate Integrated Antenna Array (SIAA).
One issue that will arise for an integrated antenna system with no access to connectors to perform legacy testing is that testing requirements such as, for example, output power, Error Vector Magnitude (EVM), and Adjacent Channel Leakage Ratio (ACLR) will not always be feasible using traditional testing schemes, i.e., conducted testing that utilizes connectors or cables to each transceiver chain. Conducted testing schemes are also referred to herein as connector-based testing schemes. One alternative testing scheme is a radiated testing scheme such as a testing scheme that utilizes an anechoic test chamber. However, radiated testing such that those using an anechoic test chamber require long test times since each antenna element must be tested separately. In addition, radiated testing schemes do not isolate specific antenna elements or transceiver chains in order to investigate broken or degraded antenna elements or transceiver chains.
While conducted testing schemes may be used to separately test transceiver chains, these testing schemes require separate physical connectors to each transceiver chain. However, a conducted testing scheme would be more challenging for SIAAs having a large number of transceiver chain and associated physically small antenna elements since physical connectors to each individual transceiver chain would be challenging. Further, a conducted testing scheme usually requires disconnecting the antenna element from the radio analog parts. Although this test enables observations of the individual radio parts, it introduces undesirable, lossy, and complex circuits. Also, since the antenna elements are disconnected, the conducted testing scheme does not include the antenna elements as part of the test and, therefore, does not provide test coverage of the antenna element.
Even if connector-based test mechanisms are possible, they may not be the best solution for an SIAA or other antenna integrated radio. At higher frequencies (millimeter wave), connector-based test mechanisms are difficult to implement. Further, the connectors provide unnecessary loss, and this loss has a larger impact at high frequencies. Still further, at times, the connectors utilized for the connector-based testing mechanism can be larger in size than the antenna element itself; therefore, the connector-based testing mechanism can be a bulky solution. In some implementations (e.g., mmWave), the needed connector type or size may not exist or may be challenging to manufacture.
Thus, connector-less testing mechanisms for testing an SIAA, e.g., during design and manufacturing, are desired. However, as noted above, conventional over-the-air testing mechanisms are less than ideal because, e.g., they require longer test times, which is particularly problematic as the number of antenna elements increases as the system would have to cycle through testing each antenna element on its own. Therefore, there is a need for a connector-less testing mechanism that enables testing of individual antenna elements and/or radio signal paths for an SIAA and, in particular, an SIAA that includes an antenna array including a large number of antenna elements such as those used for millimeter wave frequencies.